High Precision Hy-CI Variational Calculations for the Ground State of Neutral Helium and Helium-Like ions
James S. Sims, Stanley A. Hagstrom
Hylleraas-Configuration Interaction (Hy-CI) method variational calculations with up to 4648 expansion terms are reported for the ground 1S state of neutral helium. Convergence arguments are presented to obtain estimates for the exact nonrelativistic energy of this state. The nonrelativistic energy is calculated to be -2.9037 2437 7034 1195 9829 99 a.u. Comparisons with other calculations and an energy extrapolation give an estimated nonrelativistic energy of -2.9037 2437 7034 1195 9830(2) a.u., which agrees well with the best previous variational energy, -2.9037 2437 7034 1195 9829 955 a.u., of Korobov (Phys Rev A 2000, 61, 64503), obtained using the universal (exponential) variational expansion method with complex exponents (Frolov, A.M.; Smith, V.H. Jr. J Phys B Atom Mol Opt Phys 1995, 28, L449). In addition to He, results are also included for the ground1S states of H-, Li+, Be++, and B+3.
B+3 ground state energy, Be++ ground state energy, CI-HY variational calculation high preci, H-ground state energy Li+ ground state e, helium ground state calculation, HY-CI variational calculation, Hylleraas-configuration interaction
and Hagstrom, S.
High Precision Hy-CI Variational Calculations for the Ground State of Neutral Helium and Helium-Like ions, International Journal of Quantum Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=150834
(Accessed December 9, 2023)